Under certain conditions
It can be a way to get new business. This falls under the discussion of FREE SERVICE which should be done ONCE and only ONCE as a door opener. I found a new client about 0.5 miles away from my home by doing that. If the questions are easy, fine. If they involve severe tech analysis, the answer must be prefaced with I WOULD LIKE TO SEE THAT before offering advice, and that too is a business opener. Friends are a special case, they can be damning when it comes to invoicing - you can lose friendships over that. Family is always THERE and if you are lucky, they are few in terms of service requests and great for dinner.
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